GB2241260A - Resisting wind-lift in flat roofing - Google Patents

Abstract

Loose-laid insulation slabs 22 on a flat roof 20 are interconnected at an edge of the roof by a pair of rails 24 to form a unified edge structure and additional ballast slabs 25 are placed between the rails to resist wind-lift of the slabs 22. The ballast slabs 25 may be spaced along the sides of the roof but be abutting at the corners. The slabs 22 interengage by tongue and groove or rabbeted joints. <IMAGE>

Description

FLAT ROOFING This invention relates to flat roofing.

It is not unusual to increase the insulation value of a flat roof by laying insulating panels over the waterproof membrane. In some cases such insulation is retained against dynamic wind uplift by the use of ballast such as gravel aggregate or concrete paving slabs, or a combination of both covering the whole of the insulated roof area. The weight of such ballast normally exceeds 80 kg/m2 for aggregate and 120 kg/m2 for paving slabs. Other systems exist which rely on being loose laid over the surface of the roof and relying on self weight, an interlock of one panel to the other and additional ballast or mechanical restraint only on such parts of the surface area as are necessary. These systems offer considerable weight reduction on the roof to those described above. Of course, the panels need to be capable of bearing usual roof traffic for maintenance or customary use.They also need to be secure to resist lifting in wind. A particularly effective arrangement is to arrange for the individual panels to be separate from adjacent panels but keyed thereto (for example in the manner illustrated in Figs. 5A and 5B). When wind tends to lift these panels air pressure beneath is rapidly dissipated by the gaps between panels.

Problems can arise, however, at the edges of roofs. Figs. 1 to 4 illustrate situations in which existing methods have draw backs. In order to ensure that edge panels 10 are not subject to wind lift forces in excess of a desired maximum it has been necessary that either the edge has a parapet 11 whose height h above the top surface of panels 10 is at equal thickness t of the panels 10 when there is no gutter (Fig.4) or equal at least to the sum of t plus w (the width of a gutter 12). Where the parapet 11 is sufficiently high, this causes no problem. When the parapet is too low, or non-existent (Fig. 3 or Fig.2) it is necessary to apply a trim 13 to cover the edge panels. This can cause severe problems. For example, a trim 13 must be secured to panels 10 and to the wall 14. Securement to the roof is easy, but attachment to the wall can be difficult.In a tall building scaffolding or ladders may be needed adding costs. In the case of decorative surfaces the trim 13 may be unsightly or very expensive. Fixing to some surfaces, such as glass panels or exposed aggregate panels can be difficult if not impossible.

If there is a gutter such as 15 (Fig.3) it is impossible to fit a trim 16 without interfering with gutter function.

An object of the invention, therefore, is to provide an improved flat roof construction.

The invention provides a flat roof construction including insulation panels laid loose on top of a roof structure, edge portions of the roof being provided with means extending alongside the roof edge and secured to the panels to unite them and ballast weighting panels in the edge zone towards the roof structure.

The invention also provides a roof construction including a roof base overlaid by an array of loose-laid insulation panels, selected said panels in an edge zone of the roof being connected to form a unitary structure resistant to flexing, and ballast urging the structure downards.

The panels can be united by means of a frame and separate ballast. Alternatively, heavy frame members can provide simultaneous connection and ballast.

Desirably, the uniting is effected by frame members as of angle iron and the ballast can be paving slabs or similar.

Said means can be a frame.

The frame means can be a pair of parallel members extending parallel to the roof edge.

Ballast can lie between the members. The frame member can be of any convenient material such as timber plastics or metal, provided they are resistant to significant bending. Metal is preferred. Angle iron T-section bar, or tube can be used.

Ballast can be lead, metal stone or concrete, or, indeed, any material which is heavy enough and relatively unmovable. Paving slabs of concrete are preferred. The ballast is best held or desirably secured to the frame members to resist creep and/or removal.

The outer frame member 6 and ballast need to be as near to the edge as possible to have maximum loading effect. However, it is desirable that the inner frame member 6 lies over a row of panels which is not an edge row, to spread the ballasting effect over a wider panel area. Particular advantages are obtained with a herringbone pattern of panels, wherein some lie in rows, an edge row beneath the outer frame member and a penultimate row beneath the inner frame member.

Desirably, some of the panels are connected to both frame members to form a unitary structure.

In the case of a roof having only one exposed edge the frame can be constituted by a pair of rails.

In the case of a roof with four edges (rectangular) the frame can be two rectangular members, one inisde the other.

The invention will be described further, by way of example, with reference to the accompanying drawings wherein Figs. 1 to 4 are fragmentary cross-sectional views illustrating various roof edge formations demonstrating prior art.

Fig. 5 is a similar view illustration a preferred roof construction of the invention; Figs. 5a and 5b are enlarged details of the roof construction of Fig. 5, the portions illustrated in Figs. 5a and 5b being, however, also part of the prior art.

Fig. 6 is a plan view of an entire roof construction according to the invention; and Fig. 7 is a plan view on an enlarged scale of part of the roof of Fig. 6.

A preferred roof construction of the invention consists of an existing roof structure 20 (Fig. 5) which may, for example, consist of a concrete base together with overlying layers of bitumen or comparable waterproofing material. The roof structure may have a minimal parapet as indicated at 21 or can have a gutter such as that shown in Fig. 1 or Fig. 3.

Alternatively the roof may be completely flat as indicated in Fig.2. One common way of insulating such roofs is to lay relatively heavy traffic/insulating panels 22 loose on top of the roof. Such panels can be from 50 to 150mm or more in thickness and although their construction is not of particular relevance to this invention, a particularly common form of such panels consist of a lower layer of insulating material such as foam overlaid by a wear layer of concrete or comparable material 22b. The panels 22 have a good insulation value and are restrained or weighted to prevent being blown off by the strongest winds. In a particularly advantageous arrangement the panels are laid with gaps there between.Thus, if an edge panel lifts slightly and allows wind to enter beneath it, the whole layer of panels cannot be lifted by wind pressure, because as soon as any panel lifts pressure can be reduced through the gaps 23 which are shown in Figs. 5a and 5b. It will be seen that the interlock provided between the panels 22 will not allow an individual panel to lift without engaging and lifting its neighbours. This interlocking gives the whole roof an integral strength and resistance to wind lifting, which obviates the need for securement of the panels to the roof with the attendant problems of roof piercing and waterproofing.

As has been mentioned, however, panels at the edges of roofs are vulnerable to lifting by wind and it has been usual to specify that unless there is a parapet of sufficient height and the edge of the boundary panels can be placed close to that parapet it is necessary that the edge panel be either secured to the roof or covered by a trim such as the trim shown in Fig. 2.The disadvantages of such trims have been discussed previously.

In the construction of the present invention means are provided which engage selected ones of the panels 22 and unite them to form a coherent edge structure. The addition of ballast to this edge structure creates a roof construction which is extremely resistant to wind raising and which does not require the provision of a trim at the roof edge.

Further, the construction is relatively simple and cheap.

In the described embodiment the panels in the edge zone are held down by frame means which is in the form of a pair of parallel members 24. The members 24 are, in fact, lengths of 38mm x 38mm steel angle.

However, any other convenient frame forming material can be used, provided that it is resistant to longitudinal flexing and can be simply secured to the panels 22. Fig. 6 shows how the pieces of angle iron 24 can extend around all four sides of a rectangular roof structure and be united with each other at the corners.

In combination with the means for uniting the panels 22, there is usually a certain amount of ballast which holds down the united edge portion of the panels and resists lifting in wind. The ballast can be used anywhere on the united portion of the edge panels, and need not be directly in contact with or adjacent the frame member. It will be appreciated, of course, that if the ballast is placed within the frame members, more ballast will have to be used because it has less effect the further it is from the edge.

Comparably, if the ballast is used between the frame and the edge of the roof it is more effective and less weight is necessary. However, in this instance there is always the danger that the ballast can creep or become dislodged and fall from the roof with the possibility of danger to passers-by or loss of effectiveness. Therefore, it is desirable that the ballast is used in combination with the frame members and, desirably, within the frame members. As mentioned elsewhere, the ballast can take any form, but conveniently is constituted by paving slabs 25/26 disposed between the frame members. AS best seen in Figure 6, more ballast is required at the corners and there paving slabs are laid close together as at 26.

Over the rest of the length of the roof paving slabs are spaced apart as at 25.

Steel angle members 24 are secured to the panels 22 by means of bolts or comparable fixings. In the case of insulating panels in accordance with the Figures 5A/5B structure, the members 24 are conveniently fastened by cavity fixing members 27 which, as shown schematically in Fig. 5, can pass through the hard outer layer 22b of the panel and expand within the softer foam layer 22a securely to unite the angle members 24 thereto. Here, it should be mentioned that over long roofs, the members 24 should be provided with expansion joints which allow the members 24 to expand and contract firmly, whilst not reducing their resistance to flexing. This can conveniently be achieved by appropriately spaced gaps at which there is a sliding male/female connection, such as a bolt-like connection between the two parts.

As is best seen from a consideration of Fig.7, the combination of the members 24 and the panels 22 provides a unified border area of the roof in which the panels 22 are united. Thus, it will be seen that panels 28 and 29 are secured simply to the outermost frame member which extends parallel to the roof edge.

In a similar way panels 31 and 32 are secured only to the inner rail 24. However, at intervals of four panel widths, there is a panel 33 which bridges the two rails and unites them in the manner of a railway track. This interconnection, together with the desired Fig. 5A/B interconnection between the individual panels 28,29,31,32 between the panels 33 forms a unitary area of the panels 22. Further, the projecting panels 32 have a portion thereof which is interlocked with adjacent panels 34,35 and 36. This extends the rigidifying effect of the edge portion further towards the centre of the roof and ensures that the influence of the rail structure extends further inwards of the edge than otherwise would be the case. This is a particular advantage which is used by combining the present invention with the interlock system.

As has been mentioned, the ballast is very conveniently in the form of paving slabs 600mm square and from 50 to 100mm in depth. By using paving slabs as ballast, a very cheap and convenient form of ballast is used which is usually sized so as to be easily portable. By placing the ballast between the rail members it is discouraged from creep due to vibration in wind or due to frost. A small amount of cement or similar grout between the slab and the rail can make it very resistant to accidental or intentional removal.

The construction of the invention provides a particularly cheap and simple method of ensuring that a loose laid insulation layer on top of a roof does not give rise to problems with wind lifting and can safely be left without a parapet or edge trim.

The invention is not limited to the precise details of the foregoing and variations can be made thereto. For example, the material making up the frame can be of any convenient form. Frame members of plastics, wood and/or other material can be used provided they are sufficiently stiff and can easily be fastened to the panels. Instead of angle section T-sections, steel-sections or tubular-sections could be used. The ballast could be blocks of any material of sufficient density and ease of portability such as metal blocks or even loose aggregate where circumstances so permit, or perhaps bags of loose aggregate if necessary. It is, however, desirable that material should not be loose or movable under the influence of rain or other factors.

Instead of the two parallel rail arrangement the means holding the panels together could take any convenient form such as a light weight lattice of metal connected to the various panels and provided with sufficient stiffness to resist longitudinal bending. Again, the choice of ballast can be made.

As a possible variation, ballast and frame could be combined by using elongate concrete or comparable dense members which have both rigidity to act as the securing frame and also sufficient weight to act as the ballast.

Many other variations are possible.

Claims (15)

1. A roof construction including insulation panels laid loose on top of a structure an edge portion of the roof being provided with means extending alongside the roof edge and secured to the panels to unite them and ballast panels in the edge zone uring the panels downwards.

2. A roof construction including a basic roof structure overlaid by an array of loose-laid insulation panels, selected said panels in an edge zone of the roof being connected to form a unitary body resistant to flexing, and ballast urging the body downwards.

3. A construction as claimed in claim 1 or claim 2 wherein the panels are united by means of a frame and the ballast is separate from the frame.

4. A construction as claimed in claim 1 or claim 2 wherein heavy frame members provide simultaneous connection and ballast.

5. A construction as claimed in claim 2 or claim 3 wherein union is effected by frame members and the ballast is paving.

6. A construction as claimed in claim 5 wherein the frame members are of angle-iron.

7. A construction as claimned in claim 5 or claim 6 wherein the frame means is a pair of parallel members extending parallel to the roof edge.

8. A construction as claimed in any of claims 5, 6 or 7 wherein the ballast lies between the members.

9. A construction as claimed in any of claims 5, 6, 7 or 8 wherein the ballast is concrete paving slabs.

10. A construction as claimed in any of claims 5, 6, 7, 8 or 9 wherein the ballast is secured to the frame to resist movement and/or removal.

11. A construction as claimed in any of claims 5 to 10 wherein an inner of the the frame members lies over a row of panels which is not an edge row.

12. A construction as claimed in claim 11 wherein the panels lie in a herringbone pattern wherein some lie in an edge row beneath the outer frame member and a penultimate row lies beneath the inner frame member.

13. A construction as claimed in any of claims 5 to 12 wherein selected ones of the panels are connected to both frame members.

14. A construction as claimed in any of claims 5 to 12 and having four edges, the frame comprising two rectangular members, one inside the other.

15. A construction substantially as hereinbefore described with reference to and as illustrated in Figs. 5 and 7 of the accompanying drawings.